verb. TO KOOS, to make out, have sex with, or otherwise show romantic interest in another person.
adj. KOOSABLE, someone who is, in the point of view of the speaker, a good candidate for potential romantic action.
The beauty of the word lies in its flexibility.
verb. See that girl? I totally want to koos her.
adj. I think Martin's cool and all, but to me he's just not koosable.
(Hence being koo!)
Person B would then have licence to say: "Very Koo!"
Köö can be also used as a part of a word, such as "öököö", meaning OK.
Captain Kirk's name is also sometimes spelt "Köök".
In fact, köö can mean anything.
Someone with handle "Kissa" invented the word 'köö' and it was first used in the IRC-channel #comrades in Quakenet, from where it started to slowly spread around. #comrades is still the main place of 'köökötys' (=kööking)